1. Field of the Invention
This invention relates to the field of stethoscopes, and especially to medical stethoscopes designed for auscultation. Specifically, the invention relates to stethoscopes which will be used in the audio output frequency transmission range of about fifty cycles per second to about three thousand cycles per second (Hertz).
2. The Prior Art
In my previous patent U.S. Pat. No. 3,570,625 I have disclosed and claimed a stethoscope which is comprised of a stethoscope head, a trunk tube with a common air passage and a pair of binaural tubes connected by a binaural yoke and spring. Each end of the binaural tubes terminates in an ear piece or tip. A slot within one of the binaural tubes is close to one of the ear tips and provides a means of connection and communication between the trunk tube and one of the binaural tubes through an L-junction. Thus, the trunk tube is in series with the binaural tubes leading from the first ear piece to the second ear piece. The length of the respective air columns is preferably in the ratio of one to two.
According to another preferred embodiment, the same general design of the stethoscope is maintained with the common trunk tube replaced with individually separate air columns leading from the stethoscope head to each ear piece. The theory behind this design was to create a condition through the frequency range wherein the intensity curves at the right and left air columns are complementary. That is, when the intensity curve of the air tube of the right ear begins to fall off, the intensity curve of the air tube of the left ear is rising. In actual practice, the stethoscope design was found to actually produce intensity peaks which for the most part occurred at the same place so that such peaks were not complementary. Furthermore, the stethoscope design was found to be next to impossible to manufacture because the design precluded the production of an airtight sound sealed air tube.
After considerable research, including new designs as well as sound transmission testing, I have developed a new and novel stethoscope design which is characterized by sound transmission curves wherein the resonant peaks of the air column to one ear lie substantially within the resonant valleys of the air column to the other ear. Furthermore, the design of the stethoscope is practical to manufacture and assemble, being capable of being produced in a substantially airtight sound sealed condition which minimizes distortion in the sound transmission curves. Moreover, the stethoscope design of this invention permits the monitoring of frequency ranges especially in the lower ranges which were unavailable with the prior art stethoscope designs. Furthermore, in the critical range between about eighty cycles per second to about five hundred cycles per second, there is considerable enhancement of the sound transmission permitting improved monitoring of auscultation sounds